Red Hat OpenShift Administration I: Operating a Production Cluster

Instructions

1. As the developer user, create a MySQL deployment in a new project.

   1. Log in as the developer user with the developer password.

      [student@workstation ~]$ oc login -u developer -p developer \
        https://api.ocp4.example.com:6443
      ...output omitted...

   2. Create a project named deploy-workloads.

      [student@workstation ~]$ oc new-project deploy-workloads
      Now using project "deploy-workloads" on server "https://api.ocp4.example.com:6443".
      ...output omitted...

   3. Create a deployment that runs an ephemeral MySQL server.

      [student@workstation ~]$ oc create deployment my-db \
        --image registry.ocp4.example.com:8443/rhel9/mysql-80:1
      Warning: would violate PodSecurity "restricted:v1.24"
      ...output omitted...
      deployment.apps/my-db created

      Note

      It is safe to ignore pod security warnings for exercises in this course. OpenShift uses the Security Context Constraints controller to provide safe defaults for pod security.

   4. Retrieve the status of the deployment.

      [student@workstation ~]$ oc get deployments
      NAME    READY   UP-TO-DATE   AVAILABLE   AGE
      my-db   0/1     1            0           67s

      The deployment never has a ready instance.

   5. Retrieve the status of the created pod. Your pod name might differ from the output.

      [student@workstation ~]$ oc get pods
      NAME                     READY   STATUS             RESTARTS      AGE
      my-db-8567b478dd-d28f7   0/1     CrashLoopBackOff   4 (60s ago)   2m35s

      The pod fails to start and repeatedly crashes.

   6. Review the logs for the pod to determine why it fails to start.

      [student@workstation ~]$ oc logs deploy/my-db
      ...output omitted...
      You must either specify the following environment variables:
        MYSQL_USER (regex: '^$')
        MYSQL_PASSWORD (regex: '^[a-zA-Z0-9_~!@#$%^&*()-=<>,.?;:|]$')
        MYSQL_DATABASE (regex: '^$')
      Or the following environment variable:
        MYSQL_ROOT_PASSWORD (regex: '^[a-zA-Z0-9_~!@#$%^&*()-=<>,.?;:|]$')
      ...output omitted...

      Note that the container fails to start due to missing environment variables.

2. Fix the database deployment and verify that the server is running.

   1. Set the MYSQL_USER, MYSQL_PASSWORD, and MYSQL_DATABASE environment variables.

      [student@workstation ~]$ oc set env deployment/my-db \
        MYSQL_USER=developer \
        MYSQL_PASSWORD=developer \
        MYSQL_DATABASE=sampledb
      deployment.apps/my-db updated

   2. Retrieve the list of deployments and observe that the my-db deployment has a running pod.

      [student@workstation ~]$ oc get deployments
      NAME    READY   UP-TO-DATE   AVAILABLE   AGE
      my-db   1/1     1            1           4m50s

   3. Retrieve the internal IP address of the MySQL pod within the list of all pods.

      [student@workstation ~]$ oc get pods -o wide
      NAME                     READY   STATUS    RESTARTS   AGE   IP        ...
      my-db-748c97d478-g8xc9   1/1     Running   0          64s   10.8.0.91 ...

      The -o wide option enables additional output, such as IP addresses. Your IP address value might differ from the previous output.

   4. Verify that the database server is running, by running a query. Replace the IP address with the one that you retrieved in the preceding step.

      [student@workstation ~]$ oc run -it db-test --restart=Never \
        --image registry.ocp4.example.com:8443/rhel9/mysql-80:1 \
        -- mysql sampledb -h 10.8.0.91 -u developer --password=developer \
        -e "select 1;"
      ...output omitted...
      ---
      | 1 |
      ---
      | 1 |
      ---

3. Delete the database server pod and observe that the deployment causes the pod to be re-created.

   1. Delete the existing MySQL pod by using the label that is associated with the deployment.

      [student@workstation ~]$ oc delete pod -l app=my-db
      pod "my-db-84c8995d5-2sssl" deleted

   2. Retrieve the information for the MySQL pod and observe that it is newly created. Your pod name might differ in your output.

      [student@workstation ~]$ oc get pod -l app=my-db
      NAME                    READY   STATUS    RESTARTS   AGE
      my-db-fbccb9447-p99jd   1/1     Running   0          6s

4. Create and apply a job resource that prints the time and date repeatedly.

   1. Create a job resource called date-loop that runs a script. Ignore the warning.

      [student@workstation ~]$ oc create job date-loop \
        --image registry.ocp4.example.com:8443/ubi9/ubi \
        -- /bin/bash -c "for i in {1..30}; do date; done"
      job.batch/date-loop created

   2. Retrieve the job resource to review the pod specification.

      [student@workstation ~]$ oc get job date-loop -o yaml
      ...output omitted...
          spec:
            containers:
            - command: 
              - /bin/bash
              - -c
              - for i in {1..30}; do date; done
              image: registry.ocp4.example.com:8443/ubi9/ubi 
              imagePullPolicy: Always
              name: date-loop
              resources: {}
              terminationMessagePath: /dev/termination-log
              terminationMessagePolicy: File
            dnsPolicy: ClusterFirst
            restartPolicy: Never 
            schedulerName: default-scheduler
            securityContext: {}
            terminationGracePeriodSeconds: 30
      ...output omitted...

      	The command object, which specifies the defined script to execute within the pod.
      	Sets the container image for the pod.
      	Defines the restart policy for the pod. Kubernetes does not restart the job pod after the pod exits.

   3. List the jobs to see that the date-loop job completed successfully.

      [student@workstation ~]$ oc get jobs
      NAME          COMPLETIONS   DURATION   AGE
      date-loop     1/1           7s         8s

      You might need to wait for the script to finish and run the command again.

   4. Retrieve the logs for the associated pod. The log values might differ in your output.

      [student@workstation ~]$ oc logs job/date-loop
      Fri Nov 18 14:50:56 UTC 2022
      Fri Nov 18 14:50:59 UTC 2022
      ...output omitted...

5. Delete the pod for the date-loop job and observe that the pod is not created again.

   1. Delete the associated pod.

      [student@workstation ~]$ oc delete pod -l job-name=date-loop
      pod "date-loop-wvn2q" deleted

   2. View the list of pods and observe that the pod is not re-created for the job.

      [student@workstation ~]$ oc get pod -l job-name=date-loop
      No resources found in deploy-workloads namespace.

   3. Verify that the job status is still listed as successfully completed.

      [student@workstation ~]$ oc get job -l job-name=date-loop
      NAME        COMPLETIONS   DURATION   AGE
      date-loop   1/1           7s         7m36s